Hard to vote when I haven't had any problems from any of those retailers. Guess I'll throw it to Amazon because I bought the most from them without having to contact customer support.
Amazon is the best. Ordered Brutal Legend and later that day the price dropped $5. I couldn't cancel my order because items were being prepped for shipping. I sent an email and a few short hours later I had my $5 credit.
Amazon. Before Christmas they shipped me a 40" TV...when I received it there was nothing in the box! They refunded my money, and I upgraded to a better 40" TV, they matched the same sweet deal, plus $100 off the upgrade!